This invention relates to controlled release agricultural products and processes for making such products. More particularly, the present invention is directed to particulate absorbents in particulate form and holding compositions in particulate form that provide for controlled release of agriculturally beneficial materials such as fertilizers, insecticides, herbicides and fungicides. The particulate absorbents contain capillaries/voids between 10-200 microns in cross-sectional diameter and are impregnated in an amount of 40-95% of the capillaries/voids volume with the agriculturally beneficial material. The process of the present invention forms the controlled release agricultural particulate absorbents by blending the absorbent with the agriculturally beneficial material(s) for a prescribed time. The blended absorbent is fed into a granulator and after screening, the product is dried. The process results in an easily handled, free flowing, controlled release agricultural absorbent based product.
There are many slow and extended release fertilizers with their nutrient release based on time and event related coating failures or coating permeability, and/or low solubility, and/or microbial activity in the soil, and/or a ratio of surface area to nutrient weight of the particle. Of these, the major commercial products are sulfur coated urea, polymer coated ureas, and urea—formaldehyde products such as methylene ureas. The production costs of these materials vary, but all of these commercially available products have been judged by the consumers' spending patterns as too expensive for extensive use in agriculture. This especially occurs in the case of major crops such as wheat and corn which are grown on moist, dry, and irrigated soils under varying weather conditions. In addition, these high priced extended release products are in general not tailored for the short growing periods of wheat and corn because they do not release their nutrients completely within the growing period of these crops. The existing products are tailored for severe water regime nutrient applications, such as rice, sugar cane, and pineapples and high-end truck farm crops, such as strawberries, and cranberries, or shrubs, ornamentals, and flowers. When used for grasses, existing products are limited because of their high cost for use on lawns, gardens, parks, golf courses and commercial, governmental, and educational grounds. The existing products are not extensively used for pasture lands because of the added processing cost of the fertilizer. Furthermore, when existing controlled release products are used for lawn care applications, many purchasers-users primarily desire burn protection caused by overdosing the lawn while applying the fertilizer. They do not necessarily desire long term release properties that the fertilizer may provide.
Thus, a low cost alternative fertilizer with a much shorter controlled release period would be superior to the higher cost, longer controlled/extended release fertilizers.